1. Field of the Invention
The present invention relates to a method of opening and assembling flat-folded cardboard cases. The invention also relates to a machine for opening and assembling flat-folded cases, and to a mechanism for opening flat-folded cases. Throughout the following description and claims, the term "case" is used to denote a box, carton or the like.
2. Description of the Prior Art
Most corrugated cardboard cases have four panels, two pairs of top flaps, and two pairs of bottom flaps. When they are stored, their panels and flaps are folded flat. To form such a flat-folded corrugated cardboard case into an open case, the flat-folded case is first opened and shaped like a hollow cylinder, then the bottom flaps are folded and sealed, thus forming a bottomed case. Goods are packed into this case through the open top, and top flaps are folded and sealed, so that the packed goods may be shipped.
A case-assembling machine is used to open flat preassembled cases, shape them into open cases, and seal the bottom flaps of these cases. To pack goods into the cases, and to fold and seal the top flaps of these cases, a packaging machine is employed.
Of the bottom flaps of each flat preassembled case, a first pair, which are to be folded first, are called "inner flaps", while a second pair, which are to be folded next, are called "outer flaps." The same naming applies to the top flaps of the flat preassembled case. Of the four main panels of the flat folded case a first two opposing panels to which are connected the inner flaps, both top and bottom, are called "end panels", while a second two opposing panels are called "side panels."
Generally, a flat folded case is formed into an open case and sealed into a bottomed case, in the following steps:
1. First, a compressive force is applied to the flat folded case as is shown in FIG. 38(a), thereby opening same into a hollow cylinder as is illustrated in FIG. 38(b).
2. Then, the inner bottom flaps, i.e., upper-inner flap F1U and lower-inner flap F1L, are folded inward, as is shown in FIG. 38(c), and the bottom outer flaps, i.e., left-outer flap F2L and right-outer flap F2R, are folded inward onto inner bottom flaps F1U and F1L, as is illustrated in FIG. 38(d). As a result, a case, closed at the bottom and open at the top, is made as is shown in FIG. 38(e).
3. Finally, adhesive tape, gummed tape, staples, hot-melt, or other sealing means is applied to the folded outer bottom flaps F2L and F2R, thereby sealing the bottom of the case, as is illustrated in FIG. 38(f).
As has been described, a flat folded case is opened, shaped and sealed. Outer bottom flaps F2L and F2R tend to open by themselves immediately after they have been folded inward as is shown in FIG. 38(d). Unless these outer bottom flaps are strongly held at the folded position, the case will be deformed. In order to prevent such deformation of the case, both outer bottom flaps F2L and F2R are held together, with their opposing edges abutting on each other, while the sealing means such as adhesive tape is being applied to the abutting edges of flaps F2L and F2R. If the opposing edges of these outer flaps are spaced apart while the sealing means is being applied, the case will not only have a poor appearance, but also be insufficiently strong.
According to JIS (Japanese Industrial Standards), flat, corrugated cardboard cases are classified into A type, B type, and C type. The A type is sub-classified into A-1 to A-5 types; the B type is sub-classified into B-1 to B-6 types; the C type is sub-classified into C-1 to C-3 types. Of the cases of these sub-classes, the A-1 type case is the most popular.
As is illustrated in FIGS. 39 and 40, inner flaps F1 of the A-1 type case have a width f1, and outer flaps F2 thereof have a width f2. Widths f1 and f2 are equal, and are half the width W of the case. Namely, f1=f2=W/2. Therefore, when outer flaps F2 are folded inward onto inner flaps F1 already folded inwardly, their opposing edges abut on each other, and extend along the center line of the case. When sealing means, such as adhesive tape, is applied to the abutting edges of outer flaps F2, it also extends straight along the center line of the case. Hence, the bottom of the case is sealed strongly, and the sealed bottom looks tidy. This is the reason why the A-1 type case is used more commonly than any of the other types.
As for the other flat A type cases, i.e., the A-2 to A-5 type cases, the inner flaps F1 and outer flaps F2 have the following relationship with the width W and length L of the cases:
A-2 Type Case: f1=f2&gt;W/2 PA0 A-3 Type Case: f1=L/2, f2=W/2 PA0 A-4 Type Case: f1=f2=L/2 PA0 A-5 Type Case: f1=f2&gt;L/2
In the case of the A-3 type case, the abutting edges of the outer flaps extend along the center line of the case, as can be understood from FIG. 40. Therefore, the case-assembling machine designed for the A-1 type case can be employed also to assemble the A-3 type case, though the A-3 type case is used in less numbers than the A-1 type case.
The corrugated cardboard cases of the sub-classes of each type are commercially available, which are different in length L, width W, and depth D. The case-assembling machine for the A-1 type case is generally considered to be a standard one, whereas the machines for assembling any other types of cases are regarded as custom-made ones. The A-1 case-assembling machine needs to be versatile enough to make the A-1 cases of various sizes. In addition, the case guiding mechanism, case opening mechanism, flap-holding mechanism and case-sealing mechanism of the A-1 case-assembling machine must be adjusted such that they can open, shape, and seal A-1 type cases of different sizes. Here arises a problem with the conventional case-assembling machines, as will be explained below.
The conventional case-assembling machines, including those for assembling A-1 type cases, have a belt conveyor for transporting flat folded preassembled cases. While each flat folded case is being transported, it is first opened, then shaped, and finally sealed. More specifically, as is shown in FIG. 40, the flat folded case is loaded on the conveyor belt, with its two outer flaps of each pair, facing upward and downward, respectively. Obviously, the flat folded case for a case of a specific type has a width different from that of the flat folded case for a case of another type. Hence, to assemble cases of any other type than those which the machine has been assembling, the case guiding mechanism, the case opening mechanism, the flap-folding mechanism, and the sealing mechanism must be aligned to the center line of the folded cases for the cases of the other type. It usually takes a long time to align these mechanisms with the center line of the folded cases for the other type cases. The operation efficiency of the case-assembling machine is inevitably low. Since the machine repuires a device for aligning these mechanisms with the center line of the flat folded cases for any type case which the machine can assemble, the machine is rather complex, large, and heavy. In other words, if the machine is versatile enough to assemble cases of various types and sizes, it cannot be compact or light.
The method of assembling corrugated cardboard cases by means of the conventional machine described above gives rise to trouble in the process of holding the flaps of the cases. As can be seen from FIGS. 38(b) and 38(c), either inner flap F1 cannot be folded inward if either or both of the outer flaps F2 have been closed very little. When either inner flap is folded inward, with either or both outer flaps F2 closed, the inner flap F1 abuts on outer flap or flaps F2, and is interposed, as a bridge, between outer flaps F2. This trouble, occurring when either or both outer flaps F2 are closed, is known as "bridging." If inner flap F1 is forcedly folded inward in spite of the bridging, both the inner flap and the outer flaps will be deformed or broken, rendering the cardboard case unusable.
Therefore, a new type of a case-assembling machine has been invented which has a sensor for detecting such bridging. As soon as the sensor detects a bridging, that is, as soon as the detector detects a stress being applied to either inner flap F1, the flap-folding mechanism of the machine is automatically stopped, to thereby prevent the deformation or rupture of the case. The interruption of the flap-folding process inevitably reduces the efficiency of the case-assembling operation.
Another new type of a case-assembling machine has been developed which also has a sensor for determining whether or not either outer flap F2 is in a closing position to prevent inner flaps F1 from being folded inward, and a flap-folding mechanism first opens up the outer flaps from the closing positions and then folds the inner flaps F1 inward. The flaps cannot be folded fast, and the case-assembling efficiency is rather low. Further, due to the necessary use of the sensor and the flap-folding mechanism, which not only folds flaps but also opens them, the machine as a whole is complex in structure.